Note: Descriptions are shown in the official language in which they were submitted.
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METHOD AND APPARATUS FOR
CONCURRENTLY PROCESSING MULTIPLE CALLS IN
A SPREAD SPECTRUM COMMUNICATIONS SYSTEM
BACKGROUND OF THE INVENTION
I. Field of the Invention
The present invention relates to wireless communication. More
particularly, the present invention relates to method and apparatus for
concurrently processing multiple calls in a spread spectrum communications
system.
II. Description of the Related Art
The use of code division multiple access (CDMA) modulation techniques
is one of several techniques for facilitating communication in which a large
number of system users are present. Although other multiple access
communication system techniques are known in the art, such as time division
multiple access (e.g., TDMA and GSM), frequency division multiple access
(FDMA), and AM modulation schemes such as amplitude companded single
sideband (ACSSB), the spread spectrum modulation technique of CDMA has
significant advantages over these other modulation techniques for multiple
access communications systems. The use of CDMA techniques in a multiple
access communications system is disclosed in U.S. Pat. No. 4,901,307, entitled
"SPREAD SPECTRUM MULTIPLE ACCESS COMMUNICATION SYSTEM
USING SATELLITE OR TERRESTRIAL REPEATERS," issued Feb. 13,1990, and
U.S. Pat. No. 5,103,459, entitled "SYSTEM AND METHOD FOR GENERATING
SIGNAL WAVEFORMS IN A CDMA CELLULAR TELEPHONE SYSTEM,'
issued Apr. 7, 1992, both assigned to the assignee of the present invention.
CDMA systems are typically designed to conform to one or more
particular CDMA standards. Examples of such CDMA standards include the
"TIA/EIA/IS-95-A Mobile Station-Base Station Compatibility Standard for
Dual-Mode Wideband Spread Spectrum Cellular System," "TIA/EIA/IS-95-B
Mobile Station-Base Station Compatibility Standard for Dual-Mode Wideband
Spread Spectrum Cellular System" (collectively, the IS-95 standard), the
TIA/EIA/IS-98-A, -B, and -C standards entitled "Recommended Minimum
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Performance Standard for Dual-Mode Spread Spectrum Cellular and PCS
Mobile Stations," and "The cdma2000 standards for spread spectrum systems,"
(hereinafter, the IS-2000 standard). New standards are continually proposed
and adopted for use.
Each of the standards noted above defines a mechanism for processing a
single call between a mobile station and a base station. The mechanism is
characterized by a call processing state machine on the signaling layer (i.e.,
layer-3) that includes a number of states and a set of allowed transitions
between the states. Each state in the state machine corresponds to a
particular
state of the mobile station (or base station) with respect to the call being
processed. A transition to a new state takes place upon the occurrence of
certain specified events.
CDMA systems are originally designed to (primarily) provide voice
communication. Consequently, the call processing state machine defined by
the CDMA standards is designed to support a single call, which is typically a
voice call. For systems that conform to a particular CDMA standard and
designed to implement the call processing state machine defined by that
standard, only one call can typically be processed at any given moment, and a
new call cannot be processed until the active call is terminated. This one-
call
limitation restricts the type of services that can be provided to the user.
As modern day communication evolves, it is highly desirable to provide
enhanced communications services beyond just voice-only or data-only
communication. These enhanced services often rely on the ability of the system
to concurrently support multiple calls. For example, the ability to
concurrently
transmit voice and video (e.g., via two concurrent calls) can be used to
provide
video conferencing. For some applications, it is desirable to allow for
concurrent transmission of voice and data (e.g., transfer of a file while
carrying
on a conversation).
Thus, techniques that allow for the concurrent processing of multiple
calls in a spread spectrum environment are highly desirable.
SUMMARY OF THE INVENTION
Some embodiments of the present invention provide techniques that enable the
processing of multiple calls in a spread spectrum communications system. Some
embodiments of the
invention achieve this by modifying (or redefining) the call processing state
machine defined by the
CDMA standards (e.g., IS-95 and IS-2000) to include a ("traffic channel")
substate indicative of the
mobile station processing at least one active call. Some embodiments of the
invention further provide
call control (CC) state machines of various
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types, which are used to control the processing of the associated calls. In an
embodiment, one CC state machine is instantiated for each call to be
processed,
and the instantiated CC state machine is terminated upon the release of the
associated call. Referring to FIG. 5, Layer 3 processing state machine refers
to
the overall state machine 500, and call control (CC) state machines refer to
the
voice, data, ISDN, and GSM state machine instantiated for each call.
An embodiment of the invention provides a method for processing one
or more calls concurrently in a spread spectrum communications system. In
accordance with the method, an indication of a particular call to be processed
is
received and a CC state machine for this call is instantiated. The
instantiated
CC state machine is identified with and used to control the processing of the
particular call. Thereafter, one or more data transmissions related to the
particular call are exchanged. Upon receiving an indication of an additional
call
to be processed, another CC state machine can be instantiated for the
additional
call. Correspondingly, upon receiving a directive to release a particular
call,
the call is released and its instantiated CC state machine is terminated. In
an
embodiment, each call to be processed is associated with a particular service
option connection, which includes information indicative of a set of
parameters
(e.g., the physical channels) to be used for data transmission.
The instantiated CC state machine can be of a particular type selected
based on the type of the call being processed. For example, different CC state
machines can be used for voice, data, video, fax, ISDN, GSM, and other types
of
call. In one implementation, the instantiated CC state machine for a voice
call
includes: (1) a waiting for order substate indicative of a wait for an order
from
the base station, (2) a waiting for answer substate indicative of a wait for a
user
response to the particular call, (3) a conversation substate indicative of a
period
of permissible transmissions for the voice call, and (4) a release substate
indicative of termination of the voice call.
Another embodiment of the invention provides a method for supporting
two or more calls concurrently in a spread spectrum communications system.
In accordance with this method, an indication of a first call (CallA) to be
processed is received. A first service option connection (SO Conn,) to be used
for data transmissions is determined, and a set of one or more physical
channels is associated with the service option connection. The first call is
mapped to the first service option connection, and a CC state machine is
instantiated to control the processing of the first call. For each subsequent
call
to be processed, a separate CC state machine can be instantiated. Upon
receiving a directive to release a particular call, the call is released and
the
instantiated CC state machine for that call is also terminated.
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For the embodiments described above, when multiple, concurrent calls
are being processed, one or more additional service option connections to be
used for data transmission can be determined. Each active call is mapped to
one of the service option connections. When a call is released, a
determination
is made as to whether the service option connection of the just released call
is
used by at least one active call. The service option connection is released if
it is
not used by at least one active call. Similarly, when a service option
connection
is released, a determination is made as to whether the physical channel(s)
associated with the released service option connection are used by another
service option connection. A physical channel is released if it is not used by
at
least one active service option connection.
Yet another embodiment of the invention provides a method for processing one
or more calls in a spread spectrum communications system. In accordance with
the method, a particular communications system is selected for use and a
paging channel is monitored for an alert message of an incoming call. For each
of the calls being processed, one or more physical channels are established
for
data transmission and a CC state machine is instantiated. Messages are then
exchanged for the calls over the established physical channels. An indication
to
release a particular call is received and the instantiated CC state machine
for
the particular call is released in response to the received indication. Yet
another
embodiment of the invention provides a mobile unit that includes a controller
coupled to a receiver unit and a transmitter unit. The receiver unit receives
incoming messages and the transmitter unit transmits outgoing messages. The
controller receives an indication of a particular call to be processed,
instantiates
a call control state machine for the particular call, and exchanges one or
more
messages related to the particular call via the receiver and transmitter
units.
The instantiated call control state machine is identified with, and used to
control processing of, the particular call. The controller can further receive
an
indication of an additional call to be processed and can instantiate an
additional
call control state machine for the additional call. The controller can also
receive
a directive to release the particular call and thereafter releases the call
control
state machine for the particular call.
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An aspect of the invention provides a method for processing one or
more calls in a spread spectrum communications system, the method comprising
the
steps of: selecting a particular communications system to use; monitoring a
paging
channel for an alert message of an incoming call; and establishing one or more
physical channels for data transmission for each of the one or more calls;
wherein the
method comprises the further steps of: instantiating a call control state
machine for
each of the one or more calls upon receiving a corresponding indication to
process a
particular call, the call control state machine including a traffic channel
substate
indicative of at least one call being processed; exchanging messages for the
one or
more calls over the established one or more physical channels; receiving an
indication to release a particular call; and releasing the instantiated call
control state
machine for the particular call in response to the received indication to
release.
Another aspect of the invention provides a mobile unit in a spread
spectrum communications system comprising: a receiver unit configured to
receive
incoming messages; a transmitter unit configured to transmit outgoing
messages;
and a controller operatively coupled to the receiver and transmitter units,
the
controller configured to: select a particular communications system to use;
monitor a
paging channel for an alert message of an incoming call; and establish one or
more
physical channels for data transmission for each of the one or more calls;
wherein the
controller is further configured to: instantiate a call control state machine
for each of
the one or more calls upon receiving a corresponding indication to process a
particular call, the call control state machine including a traffic channel
substate
indicative of at least one call being processed; exchange messages for the one
or
more calls over the established one or more physical channels; receive an
indication
to release a particular call; and release the instantiated call control state
machine for
the particular call in response to the received indication to release.
BRIEF DESCRIPTION OF THE DRAWINGS
The features, nature, and advantages of the present invention will
become more apparent from the detailed description set forth below when taken
in
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conjunction with the drawings in which like reference characters identify
correspondingly throughout and wherein:
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FIG. 1 shows a diagram of a spread spectrum communications system
that supports a number of users;
FIG. 2 shows a block diagram of an embodiment of the basic subsystems
of system;
5 FIG. 3 shows a state machine for an embodiment of a mobile station call
processing;
FIG. 4 shows a state machine for an embodiment of mobile station
control on the traffic channel state;
FIG. 5 shows a state machine for an embodiment of a mobile station call
processing that can concurrently support multiple calls;
FIG. 6 is a diagram depicting the mapping between some of the
sublayers of layer-3 in accordance with an aspect of the invention; and
FIGS. 7 through 16 show diagrams of communication between the
mobile station and the base station for establishing, processing, and
releasing a
call under various conditions.
DETAILED DESCRIPTION OF THE SPECIFIC EMBODIMENTS
FIG. 1 shows a diagram of a spread spectrum communications system
100 that support a number of users. System 100 provides communication for a
number of cells 102a through 102g, with each cell 102 being serviced by a
corresponding base station 104. Various mobile stations 106 are dispersed
throughout the system. In an embodiment, each mobile station 106
communicates with one or more base stations 104 on the forward and reverse
links at any given moment, depending on whether the mobile station is in soft
handoff. The forward link refers to transmission from the base station to the
mobile station and the reverse link refers to transmission from the mobile
station to the base station. As shown in FIG. 1, base station 104a transmits
data
to mobile stations 106a and 106j on the forward link, base station 104b
transmits
data to mobile stations 106b and 106j, base station 104c transmits data to
mobile
station 106c, and so on. In FIG. 1, the solid line with the arrow indicates a
data
transmission from the base station to the mobile station. A broken line with
the
arrow indicates that the mobile station is receiving the pilot signal, but no
data
transmission, from the base station. The reverse link communication is not
shown in FIG. 1 for simplicity.
As shown by FIG. 1, each mobile station, especially those located near a
cell boundary, can receive data transmissions and/or pilot signals from
multiple base stations. If the measured pilot signal from a particular base
station is above a particular signal level, the mobile station can request
that
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base station be added to the active set of the mobile station. In an
embodiment,
each mobile station can receive data transmission from zero or more member of
the active set.
FIG. 2 shows a block diagram of an embodiment of the basic subsystems
of system 100. A mobile switching center (MSC) 110 interfaces with a packet
network interface 224, a PSTN 230, and base stations 104 in the system (only
one base station 104 is shown in FIG. 2 for simplicity). Mobile switching
center
110 coordinates the communication between mobile stations 106 in system 100
and other users coupled to packet network interface 224 and PSTN 230. PSTN
230 interfaces with users through the standard telephone network (not shown
in FIG. 2).
Mobile switching center 110 includes many selector elements 214,
although only one is shown in FIG. 2 for simplicity. One selector element 214
is
assigned to control the communication between one or more base stations 104
and one mobile station 106. If a selector element has not been assigned to
mobile station 106, a call control processor 216 is informed of the need to
page
mobile station 106. Call control processor 216 then directs base station 104
to
page mobile station 106.
Data source 220 contains the data to be transmitted to mobile station 106.
Data source 220 provides the data to packet network interface 224, which
receives and routes the data to selector element 214. Selector element 214
then
sends the data to each base station 104 in communication with mobile station
106. Each base station 104 maintains a data queue 240 that contains the data
to
be transmitted to mobile station 106.
In an embodiment, on the forward link, the data is partitioned into
packets that are then formatted with other control and coding bits and
subsequently encoded. Depending on the particular physical layer
implementation of the CDMA system, the encoded packet may be
demultiplexed into parallel streams and transmitted over one or more Walsh
channels.
The data is sent, in packets, from data queue 240 to a channel element
242. For each packet, channel element 242 inserts the necessary control
fields.
The data packet, control fields, check bits, and code tail bits comprise a
formatted packet. Channel element 242 then encodes one or more formatted
packets and interleaves (or reorders) the symbols within the encoded packets.
The interleaved packet is scrambled with a scrambling sequence, covered with
Walsh covers, and spread with a long PN code and short PNI and PNQ codes.
The spread data is quadrature modulated, filtered, and amplified by a
transmitter within a RF unit 244. The forward link signal is sent through an
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antenna 246 and transmitted over the air on a forward link 250. A channel
scheduler 248 located within base station 104 coordinates the communication
between mobile station 106 and one or more base stations 104.
At mobile station 106, the forward link signal is received by an antenna
260 and routed to a receiver unit within a front end 262. The receiver unit
filters, amplifies, quadrature demodulates, and quantizes the signal. The
digitized signal is provided to a demodulator (DEMOD) 264 where it is
despread with the long PN code and the short PNI and PNQ codes, decovered
with the Walsh covers, and descrambled with the identical scrambling
sequence. The demodulated data is provided to a decoder 266 that performs
the inverse of the signal processing functions performed at base station 104
(e.g., the de-interleaving, decoding, and frame check functions). The decoded
data is provided to a data sink 268. The hardware, as described above,
supports transmissions of data, messaging, voice, video, and other types of
communication over the forward link. These various types of communication
are generically referred to herein as simply "data".
System 100 supports data transmissions on the reverse link from mobile
station 106 to base station 104. Within mobile station 106, a controller 276
processes the data to be transmitted by routing the data to an encoder 272.
Controller 276 can be implemented as a microcontroller, a microprocessor, a
digital signal processing (DSP) chip, or an ASIC configured to perform the
functions described herein.
In an embodiment, encoder 272 encodes the data in accordance with a
Blank and Burst signaling data format described in U.S. Patent No. 5,504,773,
entitled "METHOD AND APPARATUS FOR THE FORMATTING OF DATA
FOR TRANSMISSION," assigned to the assignee of the present invention.
Encoder 272 then generates and appends a
set of CRC bits, appends a set of code tail bits, encodes the data and
appended
bits, and reorders the symbols within the encoded data. The interleaved data
is
provided to a modulator (MOD) 274.
Modulator 274 can be implemented in many embodiments. In an
embodiment, the interleaved data is covered with Walsh codes, spread with a
long PN code, and further spread with the short PNI and PNQ codes. The
spread data is provided to a transmitter unit within a front end 262. The
transmitter unit modulates the data, performs filtering and amplification, and
transmits the reverse link signal through antenna 246 over the air on reverse
link 252.
At base station 104, the reverse link signal is received by antenna 246
and provided to RF unit 244. RF unit 244 filters, amplifies, demodulates, and
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quantizes the received signal and provides the digitized signal to channel
element 242. Channel element 242 despreads the digitized signal with the short
PNI and PNQ codes and the long PN code, and decovers the despread data
with the proper Walsh code. Channel element 242 then reorders the decovered
data, decodes the de-interleaved data, and performs the CRC check function.
The decoded data (e.g. the voice, video, data, or message) is provided to
selector element 214 that then routes the data to the appropriate destination.
Channel element 242 may also forward a quality indicator to selector element
214 indicative of the condition of the received data packet.
The physical layer used to process data for an IS-95 compliant CDMA
system is described in further detail in the aforementioned U.S. Pat. No.
5,103,459. The physical layer of another CDMA system is described in U.S.
Patent No. 6,574,211, entitled "METHOD AND
APPARATUS FOR HIGH RATE PACKET DATA TRANSMISSION," filed
November 3,1997
System 100 can be designed to conform to any CDMA standard
currently in existence, or future standards to be adopted. Each standard
defines a mechanism for processing calls with the mobile station.
FIG. 3 shows a state machine 300 for an embodiment for mobile station
call processing. This state machine is defined by the IS-95-A standard and a
similar state machine is defined by the IS-2000 standard. Upon power-up, the
mobile station transitions from a power-up state 310 to a mobile station
initialization state 312.
In state 312, the mobile station selects a particular system to use. If the
selected system is an analog system (e.g., a GSM or TDMA system), the mobile
station transitions to a state 314 and begins analog mode operation.
Otherwise,
if the selected system is a CDMA system, the mobile station proceeds to
acquire
and synchronize to the selected CDMA system (i.e., to one or more base
stations in the selected system). Once the mobile station has acquired the
timing of the selected CDMA system, it enters a mobile station idle state 316.
In state 316, the mobile station is "on" but not active. The mobile station
monitors a paging channel on the forward link for messages from the base
station. If the mobile station is unable to receive the paging channel or if
another base station is to be added to the active set (e.g., for soft
handoff), the
mobile station returns to state 312 and acquires the base station. In state
316,
the mobile station can receive messages or an incoming call, originate a call,
perform registration, initiate a message transmission, or perform some other
actions. Upon initiating any of these actions, the mobile station transitions
to a
system access state 318.
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In state 318, the mobile station sends messages to the base station on one
or more access channels and receives messages from the base station on the
paging channel in an attempt to access the base station. The exchange of
messages is dependent on the particular type of communication (e.g., voice,
data) between the mobile station and the base station and the originator of
the
message (i.e., the mobile station or base station), and is described in
further
detail below. Depending on the outcome of the message exchange, the mobile
station can return to idle state 316 if no "active" communication is to be
performed with the base station or proceed to a mobile station control on the
traffic channel state 320 if a call with the base station is to be processed.
Prior to
the transition to state 320, the mobile station is assigned a forward traffic
channel for the call.
In state 320, the mobile station communicates with the base station using
the established forward and reverse traffic channels. Upon termination of the
call, the mobile station returns to state 312.
The state machine shown in FIG. 3 is further described in the applicable
CDMA standards (e.g., the IS-95 and IS-2000 standards). For a particular
CDMA standard, each of the states shown in FIG. 3 is defined by a state
machine that includes a number of substates.
FIG. 4 shows a state machine for an embodiment of mobile station
control on the traffic channel state 320. From system access state 318, upon
receiving the assigned forward traffic channel, the mobile station enters a
traffic
channel initialization substate 410 of state 320.
In substate 410, the mobile station verifies that it can receive data on the
forward traffic channel, begins transmitting data on the reverse traffic
channel,
and synchronizes the traffic channels between the mobile station and the base
station. The mobile station also performs a set of other functions (e.g.,
adjustment of the power control) upon entering and while in substate 410. The
mobile station then waits for an indication from layer 2 (for an IS-2000
compliant system) or from the base station (for an IS-95 compliant system)
that
the forward traffic channel has been acquired. The mobile station then
transitions to a waiting for order substate 412 if it received a call
originated
from the base station, or to a conversation substate 416 if it originated the
call.
In substate 412, the mobile station waits for an Alert with Information
Message from the base station. This message indicates how and when the
mobile station should ring the phone. If the mobile station receives the
message within a particular time period (T5,m) of entering substate 410, it
transitions to a waiting for mobile station answer substate 414.
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In substate 414, the mobile station informs the user of the incoming call
by ringing the phone in accordance with the received Alert with Information
Message. The mobile station then waits for a user response. Upon receiving
the user response (e.g., an indication of a depression of the "answer"
button),
5 the mobile station transitions to conversation substate 416.
In substate 416, the mobile station communicates with the base station
via the assigned traffic channels and in accordance with the negotiated
service
option connection, which is described in further detail below. For a data can
or
a call originated by the mobile station user, the user needs not be notified
of the
10 call and the mobile station enters substate 416 from substate 410. The
mobile
station stays in substate 416 for the duration of the call. The mobile station
transitions to a release substate 418 if it receives a command from the user
or a
release order from the base station to release the call.
Substate 418 signifies the termination of the call with the base station
and represents the end of mobile station control on the traffic channel state
320.
In substate 418, the mobile station confirms the call disconnection. Upon
confirmation, the mobile station returns to a system determination substate of
mobile station initialization state 314.
The state machines shown in FIGS. 3 and 4 are described in further
detail in the IS-95 and IS-2000 standards documents, including "TR45 Upper
Layer (Layer 3) Signaling Standard for cdma2000 Spread Spectrum Systems,"
PN-4431, July 11, 1999.
The state machine shown in FIG. 4 supports a single voice call between
the mobile station and the base station. In particular, if the mobile station
is in
conversation substate 416 (e.g., during a voice or data call) and another call
originated by the base station is received, the mobile station is not able to
return to waiting for order substate 412 to inform the user of the newly
received call. To return to substate 412, the current call would need to be
terminated and the mobile station would need to return to mobile station
initialization state 312. The single-call limitation generally prevents the
CDMA
system from offering a number of services such as video conferencing, multiple
services (e.g., voice and video), and others.
FIG. 5 shows a state machine 500 for an embodiment for mobile station
call processing that can concurrently support multiple calls. State machine
500
shown in FIG. 5 can be used in place of state machine 300 shown in FIG. 3.
State machine 500 includes a power-up state 510, a mobile station
initialization
substate 512, a mobile station idle state 516, and a system access state 518
that
correspond to power-up state 310, mobile station initialization state 314,
mobile
station idle state 316, and system access state 318, respectively, in FIG. 3.
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However, mobile station control on the traffic channel state 320 is replaced
with
a traffic state 520 that includes a traffic channel initialization substate
522, a
traffic channel substate 524, and a release substate 526.
In an embodiment, states 512, 516, and 518 are implemented similar to
states 312, 316, and 318, respectively. In an embodiment, traffic channel
initialization substate 522 and release substate 526 are implemented similar
to
that described for traffic channel initialization substate 410 and release
substate
418, respectively, in FIG. 4.
Upon power up (state 510), the mobile station selects a particular system
to use, and acquires and synchronizes to the selected system (state 512). The
mobile station then monitors the paging channel on the forward link (state
516)
for messages from the base station and can initiate one or more actions (e.g.,
receive messages or an incoming call, originates a call, performs
registration,
initiate a message transmission, and so on). Upon performing some of these
actions, the mobile station sends messages to the base station on the access
channel and receives messages from the base station on the paging channel
(state 518) to establish a traffic channel for the communication. The mobile
station then enters traffic state 520 and remains in this state while it has
at least
one pending call. Once all calls have been released, the mobile station
returns
to mobile station initialization state 512.
Upon entering traffic state 520 for the first call, the mobile station
synchronizes to the assigned traffic channel (substate 522). The mobile
station
then transitions to traffic channel substate 524 and, upon receiving the
appropriate message (e.g., a Call Setup Message), instantiates or invokes a
call
control (CC) state machine for the call. For example, the mobile station can
instantiate a voice CC state machine 530 for a voice call, a data CC state
machine 540 for a data call, an ISDN CC state machine 550 for a call with an
ISDN network, a GSM CC state machine 560 for a call with a GSM network, or
some other CC state machines for some other types of communication. The CC
state machines are used to control the processing of the associated calls.
While in traffic state 520, if another call is originated or received, the
mobile station instantiates another CC state machine for this new call. In an
embodiment, one CC state machine is instantiated for each call being
processed. The CC state machine is used to direct control of the associated
call
and to handle the call control messages related to that particular call. In
this
manner, a number of (L) CC state machines can exist at any given moment,
where L = 0, 1, 2, 3, and so on. The mobile station remains in traffic state
520 as
long as there is at least one pending call. Upon termination of each call, the
CC
state machine for that call is released and the mobile station determines
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whether the released call is the last pending call. If the released call is
the last
call, the mobile station proceeds to release substate 526.
State machine 500 (comprising states 510, 512, 516, 518, and 520) can be
used to implement a (lower) layer-3 state machine for a particular CDMA
system. State machine 500 defines the interaction between the mobile station
and the base station and is not specific to any particular call. State machine
500
can be used to concurrently support any number of calls. The CC state
machines are call specific and can be implemented based on the system
requirements. Moreover, CC state machines can be added, removed, or
modified (independent of state machine 500) to provide different and/or
additional services. The use of multiple CC state machines facilitates
independent connection and release of calls.
FIG. 6 is a diagram depicting the mapping between some of the
sublayers of lower layer-3 in accordance with an aspect of the invention. As
shown in FIG. 6, lower layer-3 includes a call control (CC) sublayer 612 that
resides on top of a service option control (SOC) sublayer 614 that further
resides on top of a radio resource control (RRC) sublayer 616. RRC sublayer
616 defines the physical traffic channels available for data transmissions.
SOC
sublayer 614 defines a set of parameters to be used for the data transmissions
such as the multiplex options, the power control, the forward link traffic
channel characteristics, and so on. Call control sublayer 612 identifies a set
of
pending calls being processed.
As shown in FIG. 6, a call (Call,,) is processed in CC sublayer 612 and
mapped to a particular service option connection (SO ConnN). In the example
shown in FIG. 6, CallA is mapped to SO Conn,, Call, is mapped to SO Conn,,
and Callc is also mapped to SO Conn2. The subscripts A, B, and C represent the
call identifiers (CALL _IDs) for the pending calls, and the subscripts 1 and 2
represent the connection references (CON_REFs) for the established service
option connections.
Each service option connection identifies one or more physical channels
to be used for data transmission. In the example shown in FIG. 6, SO Conn1 is
mapped to (i.e., utilizes) the dedicated control channel (DCCH) and the
supplemental channel (SCH), and SO Conn2 is mapped to the fundamental
channel (FCH) and the supplemental channel (SCH).
As each call is connected, a new CC state machine (denoted as CallX) is
instantiated. The instantiated CC state machine is of a type selected based on
the type of call being processed (e.g., voice, data, ISDN, GSM, and so on).
Each
CC state machine type includes a number of substates specific to that state
machine type. The CDMA system can be designed to support a number of
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different CC state machine types, and additional CC state machine types for
new call types (such as video and others) can be added as required or desired.
As indicated in FIG. 6, any number of calls can be concurrently
processed. Moreover, one call or multiple calls can be mapped to each service
option connection. The one-to-one mapping between call and service option
connection can be used to implement voice communication in conformance
with the IS-95 standard. In some instances, the reference for the service
option
connection (i.e., CON REF) can also be used as the CALL ID. In an
embodiment, to support a many-to-one mapping between call and service
option connection, a call-to-service option connection mapping is maintained
by both the mobile station and the base station. When the last call mapped to
a
particular service option connection is released, that service option
connection
can also be released. Similarly, when the last service option connection
mapped to a particular physical channel is released, that physical channel can
be released.
The service option connection (SO ConnN) defines a set of parameters to
be used for data transmission (referred to as the service option SON) and is
identified by a service option connection reference (CON_REFN). In an
embodiment, the service option connection is local to the mobile station and
the
base station.
The service option connection is negotiated via "service negotiation"
procedures. In an embodiment, while the mobile station is in traffic state
520, if
a service option connection is required to support a new call, the service
option
request and assignment are accomplished using the service negotiation
procedures. An example of such procedures is outlined in the IS-2000 standard
document. Other service negotiation procedures can also be implemented and
are within the scope of the invention.
In some embodiments, the physical channels are established through the
service negotiation. For these embodiments, the service negotiation procedures
can be designed to include request for one or more new traffic channels and
the
exchange of channel configuration information. The required physical channels
can then be connected and configured using the negotiated channel
configuration information. Upon completion of the service option negotiation
between the mobile station and the base station, the required physical
channel(s) are established and ready for transmission.
In an embodiment, a number of different types of CC state machines are
provided to support different types of call. Some example CC state machine
types include:
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= Voice : The voice CC state machine type is provided for voice, circuit
data, and some other services. Circuit data is transmitted via circuits
(i.e., dedicated links) that are established for the connection, similar to a
voice call. The signaling for circuit data is not in-band. The voice state
machine can be implemented similar to that for an IS-95 call state
machine (as shown in FIG. 4).
= Packet data : The data CC state machine type can be provided for packet
data. The implementation of this state machine can be based on the
requirements of the particular CDMA system. In one embodiment, the
data state machine can be implemented as a null CC state machine (i.e.,
no state machine) if the call control is performed via the data
transmission.
= ISDN : The ISDN CC state machine type can be provided for
communication with an ISDN network.
= GSM-MAP : The GSM-MAP CC state machine type can be provided for
communication with a GSM-MAP network.
In the specific embodiment shown in FIG. 5, voice CC state machine 530
includes four substates: a waiting for order substate 532, a waiting for
mobile
station answer substate 534, a conversation substate 536, and a call release
substate 538. Substates 532, 534, and 536 generally correspond to substates
412,
414, and 416, respectively, in FIG. 4. During termination of the voice call,
the
voice CC state machine transitions to the call release substate. Upon
termination of the voice call, the CC state machine for this call is released.
In an embodiment, to facilitate the tracking of the calls and the
processing of the instantiated CC state machines in a multiple, concurrent
call
environment, each call can be identified by a unique call identifier
(CALL_ID).
In an embodiment, the CALL_ID is "local" to the mobile station <-> mobile
switching center (MSC) path and is selected by the originator of the call.
Implementing local CALL_ID allows the same CALL_ID to be used by multiple
mobile stations concurrently. The CALL_ID can be analogized to the "Call
Reference" in ISDN and the "Transaction Identifier" in GSM systems.
Once the CC state machine for a particular call has been established,
subsequent call-specific transmissions (e.g., a Flash with Information
Message)
between the mobile station and the base station include the CALL ID so that
the transmissions can be routed to the proper CC state machine. In an
embodiment, the CALL_ID can be implied for the (IS-95) voice CC state
machine and for other CC state machines when there are no ambiguities. With
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this implementation, signaling in conformance with the IS-95 standard can be
generated, and backward compatibility with existing IS-95 systems is
maintained. When a single voice call or circuit switched data or fax call is
running, only minimal changes, if any, may be required to add a (possibly
5 optional) field to identify the type of the CC state machine (CC_Type) in
the
appropriate message. In some implementations, packet data calls may not
require CALL-IDs since the signaling is in-band.
In an embodiment, the CC state machines are defined with the capability
to support multiple calls per connection, similar to that of an ISDN network.
10 The resources to support multiple calls per connection may be provided by
the
mobile switching center, and such processing may be transparent to the mobile
station. For example, ISDN permits 3-way calls to have multiple call presence
(CALL_IDs) at the mobile station. In this case, the mobile station explicitly
handles the different call presence. However, in an ANSI-41 wireless systems,
15 the mobile switching center handles the explicit call presence and the
mobile
station uses the Flash with Information Message to signal a change in 3-way
call state to the mobile switching center. This mechanism for handling
multiple
calls per connection is further described in TIA/EIA-664.
The invention can be implemented, with slight modifications, within the
framework of the call processing state machine currently defined by the IS-95
and IS-2000 standards. Referring back to FIGS. 3 and 4, upon entering mobile
station control on the traffic channel state 320 from mobile station access
state
318 (FIG. 3), the mobile station proceeds to traffic channel initialization
substate
410, as currently performed by the IS-95 and IS-2000 standards. From traffic
channel initialization substate 410, the mobile station enters a newly defined
"traffic channel" substate. This new substate replaces waiting for order
substate 412, waiting for mobile station answer substate 414, and conversation
substate 416. One or more timers can be associated with substates 412 and 414
to provide the required time-out indicators implemented by the current CDMA
standards.
FIG. 7 shows a diagram of the communication between the mobile
station and the base station for processing a first call, which is a voice
call
received (i.e., terminated) by the mobile station. As used herein, a mobile
station terminated call is a call originated from the mobile switching center
and
received by the mobile station. While in mobile station idle state 516, the
mobile station receives from the paging channel a General Page Message that
includes a new service option SOS. The mobile station then enters system
access state 518 and responds with a Page Response Message on the access
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channel. Thereafter, mobile station receives an Extended Channel Assignment
Message (ECAM) that includes the assigned physical channel. After receiving
the ECAM, the mobile station transitions to traffic channel substate 524.
While
in substate 524, the mobile station receives a Call Setup Message, which
includes a CC state machine type (CALL_Type), a call identifier (CALL_IDX),
and a service option connection for this call (CON_REFN). For this specific
example, the CC_Type is voice. Upon receiving the Call Setup Message, the
mobile station instantiates a CC state machine 530 of the specified (voice) CC
Type.
In waiting for order substate 532 of the instantiated voice CC state
machine, the mobile station informs the user of the incoming call (e.g., by
ringing the phone) and waits for a user response. In some system
implementations, this Call Setup Message may be omitted for the first call
(i.e.,
default values can be used for CALL_ID and CON_REF) and the CC-Type can
be signaled via the ECAM. In this case, the CC state machine can be
instantiated upon entering traffic channel substate 524.
The mobile station then executes the service negotiation procedures with
the base station. In an embodiment, as part of the service negotiation
procedures, the mobile station receives a Service Request Message with a
service configuration record (SCR) that includes the newly added service
option SON. A set of service negotiation messages is then exchanged between
the mobile station and the base station in negotiating the parameters for the
call, which may include the service option number. At the conclusion of the
service negotiation, the mobile station receives a Service Connect Message
that
includes the SCR having the newly added service option SON and the
CON_REFN for the assigned service option connection.
In an embodiment, the service negotiation and the resulting
establishment of the service option connection may occur prior to receiving
the
Call Setup Message. In this case, the CON_REFN in the Call Setup Message
corresponds to the connection reference of the established service option
connection.
Upon receiving an Alert with Information Message that includes the
CALL_IDX assigned to this call, the mobile station transitions to waiting for
mobile station answer substate 534. The mobile station then rings the phone
and waits for a user response. After receiving the user response, the mobile
station sends a Connect Order that includes the CALL_IDX. The mobile station
then transitions to conversation substate 536 and may exchange the Flash with
Information Message with the base station. Data related to this call is
transmitted via the established physical channel(s). As shown in FIG. 7, the
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CALL_ID is included with each call specific message such that the message can
be properly routed and processed.
FIG. 8 shows a diagram of the communication between the mobile
station and the base station for processing a first call, which is a data call
received by the mobile station. The General Page Message, Page Response
Message, and ECAM are exchanged and processed in similar manner as
described above for FIG. 7. Upon receiving the ECAM, the mobile station
transitions to the traffic channel substate. Upon receiving the Call Setup
Message, the mobile station instantiates a CC state machine of the specified
(data) CC_Type and the CC state machine is placed in the conversation
substate. The mobile station also executes the service negotiation procedures
with the base station in similar manner as that described above. Upon
completion of the service negotiation, the mobile station receives data
transmission from the base station via the assigned physical channel(s).
FIG. 9 shows a diagram of the communication between the mobile
station and the base station for processing a first call, which is a voice
call
originated by the mobile station. While in mobile station idle state 516, the
mobile station receives a call connect request from the user. In response, the
mobile station sends an Origination Message that includes, for example, the
physical channel, the new service option SON, a request for a particular type
of
CC state machine (CC Type Req), the CALL _IDX, and information on the dialed
digits. The mobile station then receives an ECAM that includes the assigned
physical channel.
Similar to FIG. 8, upon receiving the ECAM, the mobile station
transitions to the traffic channel substate. Upon receiving the Call Setup
Message, the mobile station instantiates a CC state machine of the specified
(data) CC_Type and the CC state machine is placed in the conversation
substate.
FIG. 10 shows a diagram of the communication between the mobile
station and the base station for processing a first call, which is a data call
originated by the mobile station. The diagram for the mobile station
originated
data call is similar to that for the mobile station originated voice call in
FIG. 9,
except that the mobile station instantiates a data CC state machine 540 after
receiving the Call Setup Message. Upon completion of the service negotiation,
the mobile station sends data via the assigned physical channel(s).
FIG. 11 shows a diagram of the communication between the mobile
station and the base station for a subsequent (i.e., L>_2) call, which is a
voice call
received by the mobile station. The mobile switching center sends a call
connect request and, in response, the base station sends a Call Setup Message
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that includes, for example, the CC Type, the CALL_IDX, and the CON_REFN.
Upon receiving the Call Setup Message, the mobile station instantiates a CC
state machine 530 of the specified (voice) CC Type and indexed by the
specified
CALL_IDX. The mobile station performs a mapping between the CALL_IDX
and the CON_REFN.
For this new voice call, the mobile station transitions to waiting for order
substate 532 and can perform the service negotiation procedures. The mobile
station receives a Service Request Message that includes the new service
option
SON for this call. Upon completion of the service negotiation, the mobile
station
receives a Service Connect Message with the service configuration record that
includes the assigned SON, CON_REFN, and other relevant parameters. The
subsequent communication between the mobile station and the base station
proceeds in similar manner as that described above in FIG. 7 for the first
voice
call. Messages to this voice call and other calls (with the possible exception
of
the first call) are identified by the CALL_ID assigned to the call. Data calls
may
use in-band signaling.
FIG. 12 shows a diagram of the communication between the mobile
station and the base station for a subsequent (i.e., L>_2) call, which is a
voice call
originated by the mobile station. While in traffic channel substate 524, a
call
connect request is received from the user. In response, the mobile station
sends
a Call Setup Request Message that includes, for example, the requested CC type
(CC Type Req) and the CALL_IDX assigned to this call. In an embodiment, the
originator of the call (in this case, the mobile station) is able to assign
the
CALL_ID to the new call. The mobile station then receives a Call Setup
Message that includes the assigned CC Type, the CALL_IDX, and the
CON_REFN. Upon receiving the Call Setup Message, the mobile station
instantiates a CC state machine 530 of the specified (voice) CC Type and
indexed by the specified CALL_IDX. The mobile station performs a mapping
between the CALL_IDX and the CON_REFN.
For this new mobile station originated voice call, the mobile station
transitions to conversation substate 536 and sends a Call Origination Message
that includes, for example, the dialed digits and the CALL_IDX. The mobile
station then performs the service negotiation procedures. In an embodiment,
the service negotiation may occur prior to the mobile station sending the Call
Origination Message from the conversation substate. The service negotiation
messages includes the new service option SON and relevant parameters. Upon
completion of the service negotiation, the mobile station receives a Service
Connect Message with the service configuration record that includes the
assigned SON, CON_REFN, and relevant parameters. The Flash with
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Information Messages may be exchanged between the mobile station and the
base station, in similar manner as that described above for FIG. 9. Again,
messages to this and other calls are identified by the assigned CALL - ID.
FIG. 13 shows a diagram of the communication between the mobile
station and the base station for releasing a voice call (which is not the last
call)
by the mobile station. While in conversation substate 536 for this call, a
Call
Release Request is received from the user and, in response, the mobile station
enters call release substate 538. The mobile station then sends a call release
message that includes the CALL_IDX of the call to be released. In response,
the
mobile station receives a Call Release Confirmation Message that includes the
CALL_IDX. The CC state machine for this voice call is also terminated.
If the release of this call eliminates a service option connection
(determined by reviewing the call-to-service option connection mapping), the
service negotiation procedures are executed and service option connection
related messages are exchanged between the mobile station and the base
station. The mobile station transmits a Service Request Message with the
service configuration record that includes the CON_REFN to be released. At the
conclusion of the service negotiation, the mobile station receives a Service
Connect Message that includes the CON_REFN to be released. Similarly, the
physical channel can be released if not needed to support any pending call.
FIG. 14 shows a diagram of the communication between the mobile
station and the base station for releasing a voice call (which is not the last
call)
by the mobile switching center. While in conversation substate 536 for this
call,
a call release request is received by the base station and, in response, a
Call
Release Message that includes the CALL_IDX of the call to be released is
transmitted to the mobile station. Upon receiving the Call Release Message,
the
mobile station enters call release substate 538. The mobile station then sends
a
Call Release Confirmation Message that includes the CALL_IDX of the call to be
released.
If the release of this call eliminates a service option connection, the
service negotiation procedures are executed and service option connection
related messages are exchanged between the mobile station and the base
station. The mobile station receives a Service Request Message with the
service
configuration record that includes the CON_REFN to be released. At the
conclusion of the service negotiation, the mobile station receives a Service
Connect Message with the service configuration record that includes the
CON_REFN to be released. Similarly, the physical channel may be released if
not needed to support any pending call.
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FIG. 15 shows a diagram of the communication between the mobile
station and the base station for releasing the last voice call by the mobile
station. While in conversation substate 536 for this call, a call release
request is
received from the user. In response, the mobile station enters call release
5 substate 538 and sends a Call Release Message that includes the CALL - 1D,,
of
the call to be released. The mobile station then receives a Call Release
Confirmation Message that includes the CALL_IDX. Since this is the last call,
the service option connection and the physical channel for the call can be
released via an exchange of radio resource control (RRC) related messages. In
10 particular, the mobile station sends a Release Order. The mobile station
then
receives a Release Order in response and, thereafter, returns to mobile
station
idle state 516.
FIG. 16 shows a diagram of the communication between the mobile
station and the base station for releasing the last voice call by the mobile
15 switching center. While in conversation substate 536 for this call, a call
release
request is received by the base station and, in response, a Call Release
Message
that includes the CALL_IDX of the call to be released is sent to the mobile
station. The mobile station then enters call release substate 538 and sends a
Call
Release Confirmation Message that includes the CALL_IDX. Since this is the
20 last call, the physical channel used for the call can be released via an
exchange
of RRC related messages, in similar manner as that described above for FIG.
15.
The mobile station then returns to mobile station idle state 516.
FIGS. 7 through 16 show a set of diagrams that illustrates specific
implementations of the call processing by the mobile station and base station
in
accordance with an aspect of the invention. Different types and combinations
of messages can be used to effectuate the call processing, and this is within
the
scope of the invention.
The elements in the base station and mobile station described above can
be implemented in various manners. The receiver and transmitter units of the
mobile station and base station can be implemented in one or more integrated
circuits, discrete components, or a combination thereof. The controller of the
mobile station can be implemented in one or more integrated circuits, an
application specific integrated circuit (ASIC), a digital signal processor
(DSP), a
controller, a microprocessor, other circuits and/or software designed to
perform the functions described herein, or a combination thereof. The other
elements of the mobile station and base station can be implemented with a
combination of hardware and software in a manner known in the art.
The invention described herein can be applied to many spread spectrum
communications systems. The invention is applicable to spread spectrum
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systems that currently exist and new systems that are continually being
considered. A specific CDMA system is described in the aforementioned U.S.
Patent No. 6,574,211. Another CDMA system is disclosed
in the aforementioned U.S. Patent Nos. 4,901,307 and 5,103,459.
The foregoing description of the preferred embodiments is provided to
enable any person skilled in the art to make or use the present invention.
Various modifications to these embodiments will be readily apparent to those
skilled in the art, and the generic principles defined herein may be applied
to
other embodiments without the use of the inventive faculty. Thus, the present
invention is not intended to be limited to the embodiments shown herein but is
to be accorded the widest scope consistent with the principles and novel
features disclosed herein.
